1. Field
This disclosure relates generally to photovoltaic systems, and more specifically, to improving light gathering efficiency of three-dimensional solar cells.
2. Related Art
Conventional solar cells present a flat surface to incident light. One drawback of flat solar cells is that a significant portion of the incident light is reflected, which reduces the amount of light energy absorbed by the solar cell. Further, the photovoltaic coating of a flat solar cell must be thick enough to capture photons of the incident light. The energy of the photons liberates electrons from the photovoltaic materials to create an electrical current with each mobile electron leaving behind a “hole” in the atomic matrix of the photovoltaic coating. The longer it takes for electrons to exit the photovoltaic material (i.e., to flow in a conductive material), the more likely it is for the electron to recombine with a hole. This reduces electrical current generated by the solar cell.
Three-dimensional solar cells provide some solutions to the above drawbacks of conventional solar cells. Rather than presenting a flat surface to incident light, a three-dimensional solar cell presents a brush-like surface of nano-scale tower structures. These tower structures can trap and absorb light received from many different angles, thereby remaining efficient even when incident light is arriving at a significant angle to the plane of the solar cell. In addition, the photovoltaic coatings of the tower structures can be made thinner, which reduces a likelihood that electron-hole recombination can take place.
One reason that three-dimensional solar cells are more efficient than flat solar cells at collecting energy from incident light is that the three-dimensional solar cells present more surface area to capture the incident light then do the flat solar cells. If the light gathering surface area of the nano-scale tower structures is increased, then the light gathering efficiency of three-dimensional solar cells can also be increased.
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